The present invention relates to telecommunications and more particularly to signaling systems that communicate information about features of services and calls in virtual private networks.
Many corporations and other enterprises are installing private networks to interconnect their facilities to provide voice and data communications. Private networks typically include a number of private branch exchanges (PBXs) or other telephone switches that are linked together. Each PBX, which supports a private network or subnetwork of its own, is typically responsible for telecommunications services in a geographically restricted area, for example, at a particular building or campus occupied by the enterprise. In contrast to a public switched telephone network (PSTN), which is operated by a common carrier, a private network is generally characterized by access limits or restrictions, for example, by designating particular telephones or telephone numbers for internal communications only. As enterprises expand to include an increasing number of offices and sites, they need to link together the PBXs and private networks across wider geographical areas.
FIG. 7(a) depicts one way of linking private networks 700 and 710 together by installing a fixed, point-to-point private line 720 between the two private networks. For purposes of illustration, private network 700 includes a PBX 702 and two (2) telephones 704 and 706, and private network 710 also includes a PBX 712 and two (2) telephones 714 and 716. A fixed, point-to-point private line 720 is coupled between PBX 702 of private network 700 and PBX 712 of private network 710. Accordingly, a user of telephone 704 in private network 700 can call telephone 714 over fixed, point-to-point private line 720 in private network 710.
One drawback for an enterprise in interconnecting private networks at different sites with fixed, point-to-point private lines becomes apparent when the sites are widely separated. For example, to install a fixed, point-to-point private line beyond the boundaries of an office building or campus is often too expensive. When the sites are in different cities or different countries, the cost may become prohibitive. Accordingly, public telephone carriers offer xe2x80x9cvirtual private networksxe2x80x9d to their customers.
A virtual private network is a combination of public and private networks, in which the public portion of the virtual private network carries local and long distance communications between various private networks. In a virtual private network, as illustrated in FIG. 7(b), the customer uses the telephone carrier""s public network 730 to interconnect its geographically separated private networks 700 and 710. The network dialing plans, routing schemes, and switches of the public network 730, however, are configured in such a manner that the customer""s service appears to be carried over a private network connection. Such a configuration can actually involve the use of several interconnected networks, each of which use may employ a different signaling protocol.
One benefit of private networks over public networks is that they can provide features and services that are unavailable in public networks. A feature is a unit of functionality that is incrementally added to a network to provide an additional service to users of the network. Many PBXs that implement private networks employ various protocols to support a rich set of features. For example, DPNSS, a PBX protocol popular in the United Kingdom, offers Call-Back-When-Free, Three-Way-Calling, Call-Forwarding, and many other special features.
Many private networks, however, implement features that are generally not supported by the protocols used within common public networks and, hence, in common virtual private networks. Protocols or messages that include feature requests not supported by the public network are typically filtered out or otherwise lost at an access point in the public network, because the unsupported feature has no analogue in the signaling message structure of the public network. Although some protocols employed by public networks reserve some space in signaling messages for passing user-defined information, the available space is typically insufficient for directly supporting many features common in private networks. Consequently, calls placed from such a private network across the public network portion are usually limited to the lowest-common denominator, often Plain Old Telephone Service (POTS), thereby destroying the appearance of a wide area virtual private network.
Based on the foregoing, there is a clear need for mechanisms that permit use of advanced calling features in a virtual private network, even when the public telephone network that implements the virtual private network does not support, or have a protocol capable of supporting, features of the private network.
Further, there is a need for a method of transmitting signaling messages over a virtual private network that request features not supported by a public network that implements the virtual private network.
These needs, and other needs that will become apparent from the following description, are addressed by the present invention, which comprises, in one aspect, an auxiliary communication network connection to transmit publicly non-supported features between sites in a virtual private network connected by a public communication network. Use of the auxiliary communication network enables messages to be passed between the virtual private networks sites without having to filter out or otherwise downgrade messages due to limitations in the protocols used by the public network. Consequently, users of the virtual private network gain feature transparency, which is the virtual appearance of a full-featured private network from end to end notwithstanding the lack of capabilities of the public communication network used for call establishment.
Since public communication networks often employ complicated and sophisticated routing techniques, there is also a need for a way to establish the auxiliary network connection without duplicating the routing logic of the public network. According to another aspect, the auxiliary connection is initiated through the auxiliary communication network from the destination site to the originating site, after the destination site in the virtual private network has received a connection request message from the originating site through the public network. Preferably, the auxiliary connection is established based on an identifier of the originating site passed within a user-defined space of the connection request message. Consequently, the auxiliary connection for handling features can be established regardless of how the original call is routed through the network.
Accordingly, one aspect of the invention relates to a call feature transmission apparatus for use with a first private network that is connected to a second private network by a communication network. The communication network employs a protocol incapable of supporting at least one feature supported by the first private network and the second private network. The apparatus comprises a first communications interface coupled between the first private network and the communication network so as to communicate information between the first private network and the communication network. The apparatus also includes a second communications interface coupled between the first private network and an auxiliary network so as to communicate messages in the protocol that use the at least one feature. A processor is coupled to the first communications interface, the second communications interface, and a memory. The memory contains one or more instructions which, when executed by the processor, cause the processor to intercept a message directed from the first private network to the second private network, determine whether the message uses the at least one feature, and in response, transmit the feature request to the second private network.
Another aspect of the invention involves a telecommunications network that includes a first private network and a second private network, in which both networks are capable of supporting a feature, and a first communication network, which employs a protocol incapable of supporting the feature. A first protocol converter is coupled to the first private network and the first communication network, and a second protocol converter is coupled to the second private network and the first communication network. The first and second protocol converters are telecommunications devices capable of converting between the different protocols at least those messages for establishing a connection. A second communication network is coupled to the first and second protocol converters for supporting the feature. Preferably, the first protocol converter is configured to establish a first connection from the first private network to the second private network through the first communication network. The second protocol converter is configured to establish a second connection from the second private network to the first private network through the second communication network in response to the first connection being established.
Still another aspect involves a method of transmitting a signaling message, requesting a feature, supported by the first and second private networks, from a first private network to a second private network in a virtual private network connected by a first communication network employing a protocol incapable of supporting the feature. Accordingly, a first connection is established through the first communication network between the first private network and the second private network. In response to establishing the first connection, a second connection is established between the first private network and the second private network through a second communication network. The feature is transmitted between the first private network and the second private network through the second communication network.
Yet another aspect relates to a telecommunications device including a computer system and a computer-readable medium bearing instructions for supporting feature transparency in a virtual private network. The virtual private network includes a first private network and a second private network connected by a first communication network, which employs a protocol incapable of supporting at least one feature supported by the first and second private networks. Accordingly, a signaling message is intercepted from the first private network for the second private network. If the signaling message includes a feature request not supported by the protocol of the first communication network, then the feature request is transmitted to the second private network through a second communication network.